Synthetic composites are increasingly being used in making products for a number of different reasons. Synthetic materials are often easier to mold or otherwise fabricate into parts than other materials, and products can usually be replicated in large volume at lower cost. Additionally, synthetic materials have strength/weight ratio advantages, and require lower capital costs or initial investment. Fiber reinforced resin products now exist in wide ranging and growing variety, whether the fibers are glass, carbon, graphite, boron or of polymeric material. An important division within this broad category is that of foam-filled parts having a skin of reinforced fiber material. While foam-filled synthetic structures which have inner and outer synthetic shells that are not fiber reinforced are also well-known, fiber or filament reinforcement is demanded where greater strength and stiffness are of importance.
Important examples of the usefulness of foam-filled reinforced fiber skin parts are found in aerodynamic applications, such as front and rear wings for racing vehicles and empennage and control surfaces for aircraft. These require a high strength to weight ratio, precise conformity to shape under significant force loading, and also high impact resistance. The high velocities at which these vehicles travel mean that an impact to an aerodynamic surface which does not materially damage the remainder of the vehicle can itself have catastrophic results. Minor collisions or contacts should not result in deformation of such a component, since shape change would reduce its utility.
While some parts of this type might be made in high volume, such as a shaped wing for a production sports car, there are a number of situations in which an ability to fabricate a small number of parts without incurring high capital costs is required or desirable. For example, as racing vehicles evolve through a sequence of changes to meet competition, wing designs can change as well. Production runs of each variant may thus be quite limited. Consequently, racing teams will not keep on hand a significant inventory of such parts, forcing them to replicate a destroyed or damaged part at low cost, if possible, from an existing unit. This is seldom feasible using present day technology, particularly if such work must be done at a racing venue.
Similarly, needs exist for making airfoil structures using new methodologies in the private airplane business. Using any of a large number of available kits, private airplane enthusiasts can build their own craft and fly them without the stringent testing and certification procedures needed for production aircraft. Even with certified production aircraft, which have long life expectancy, but which may no longer be manufactured in the same model, replacement of aerodynamic parts may require replication from an existing unit. Few suppliers will tool up to manufacture one or only a few units, even though the user must of necessity pay a significant price. The ability to duplicate at low capital and process cost from an available part is thus of real significance in this field as well.
The physical integrity of a foam filled, fiber-reinforced skin part is dependent on the nature of the union between the different materials, as well as the thickness, strength and stiffness of the fiber-reinforced composite layers themselves. With superior physical properties being achievable, parts can be redesigned to take advantage of such characteristics.